Reheating furnace



Oct. 19, 1965 J. E. FOLDESSY 3,212,763

REHEATING FURNACE Filed March 5, 1964 4 Sheets-Sheet 1 INVENTOR. JUST/IVE FOLDESS) Oct. 19, 1965 J. E. FOLDESSY REHEATING FURNACE 4 Sheets-Sheet2 Filed March 5, 1964 JUS T/N E. FOL 0555 Y B A! farney Oct. 19, 1965Filed March 5, 1964 J. E. FOLDESSY REHEATING FURNACE 4 Sheets-Sheet 3INVENTOR. JUS T/N E. FOLDESS Y Attorney Oct. 19, 1965 J. E. FOLDESSY3,212,763

REHEATING FURNACE Filed March 5, 1964 4 Sheets-Sheet 4 INVENTOR. JUST/NE. FOLDESSY Attorney United States Patent Filed Mar. 5, 1964, Ser. No.349,608 4 Claims. (Cl. 2636) This invention relates to an improvedfurnace for reheating semifinished metal shapes, such as steel slabs,blooms, billets or the like.

A conventional continuous reheating furnace includes an elongatedenclosure and a set of water-cooled skids which support the work as ittravels through the enclosure. Such furnaces are equipped with one ormore recuperators which utilize sensible heat in the products ofcombustion to preheat incoming combustion air. The recuperators usuallyare located above or alongside the furnace enclosure and are a costlyadjunct to install and maintain. Water-cooling the skids takes heat fromthe furnace, and any leakage is destructive to the furnace refractory.The work usually has cool spots, known as skid marks, in areas whichcontact the water-cooled skids.

An object of my invention is to provide an improved reheating furnacewhich largely overcomes the foregoing disadvantages, that is, in whichthe skids are air-cooled, and in which air heated by contact with theskids is used as combustion air in the furnace, thus diminishing thesize of recuperators needed.

A more specific object is to provide an improved reheating furnace inwhich the skids and their supports are air-cooled in sections, and inwhich air heated in the skids is used as combustion air in the furnace,either passing through recuperators for further heating or blending withheated air from the recuperators before reaching the furnace.

In the drawings:

FIGURE 1 is a top plan view of a furnace constructed in accordance withmy invention;

FIGURE 2 is a longitudinal vertical section on line IIII of FIGURE 1;

FIGURE 3 is a horizontal section on line IIIIII of FIGURE 2;

FIGURE 4 is a vertical cross section on line IV-IV of FIGURE 2; and

FIGURE 5 is a vertical cross section on line VV of FIGURE 2.

The drawings show a continuous reheating furnace 10, which can be ofconventional construction apart from the skids and the air distributionsystem, hereinafter described. The furnace enclosure includes the usualbottom wall 12, roof 13 and side walls 14. The ends of the enclosurehave doors 15 and 16 through which work W enters and leaves the furnace.Work-supporting skids 17, constructed in accordance with my invention,extend from the entry door 15 to .a short hearth section 18 in front ofthe exit door 16. The furnace illustrated has a first heating zone 19above the skids, second and third heating zones 20 and 21 below theskids, and a soaking zone 22 above the hearth section 18, but the numberand arrangement of zones can vary. The furnace illustrated iscounterfired, and each zone has burners 23. Products of combustiondischarge through an olftake 24 in the roof 13 near the entry end andpass through a recuperator 25 above the furnace enclosure and thence outa stack, not shown. The recuperator also can be of conventionalconstruction, although preferably smaller than normally included with afurnace of any given size. A cold air main 26, equipped with a blower27, extends along one side of the recuperator for introducing cold airthereto. A hot air main 28 extends along the other side of the recuper-3,212,763 Patented Oct. 19, 1965 :ator for receiving the heated airtherefrom and carrying it to the burners 23. The burners also areconnected to a suitable fuel supply, not shown.

In accordance with my invention, I construct skids 17 in a plurality ofsections 17a, 17b and 17c placed end-toend. Each section includes aplurality of longitudinal pipes 29, a plurality of transverse pipes 30,and a plurality of supports 31. The work rests on the longitudinal pipes29, which overlie the transverse pipes 30. As FIG- URE 5 shows, eachsupport 31 is formed of a pipe of inverted U-shape, and the supports arearranged in opposed pairs under the transverse pipes 30.

A cooling air main 32, equipped with a blower 33, extends horizontallyalongside the lower portion of the furnace enclosure and has transversebranches 32a, 32b and 320 corresponding in number with the skid sections17a,

' 17b and 170. I connect the longitudinal pipes 29 at the entry end ofthe skid sections 17a, 17b and 17c to the branches 32a, 32b and 320respectively via vertical pipes 34 which extend upwardly from thebranches. I connect the other ends of pipes 29 to tranverse pipes 35 viavertical pipes 36, which extend downwardly from pipes 29. Pipes 35 arelocated immediately beneath the bottom wall 12 of the furnace enclosure,but lead upwardly at one side thereof to a collector main 37, whichextends lengthwise of the enclosure near the cold air main 26. I connectone end of each transverse pipe 30 of the skid sections to the coolingair main 32 via respective vertical pipes 38 which extend upwardly fromthe main. I connect the other end of each pipe 30 to the collector main37 via vertical pipes 39 which extend both upwardly and downwardly frompipes 30. I connect opposite ends of the supporting pipes 31 to thecooling air main 32 and to the vertical pipes 39 via horizontal pipes 40and 41 respectively, arranged as shown in FIGURE 5.

I connect the collector main 37 to the cold air main 26 via a connectingmain 42. I also connect the collector main to the hot air main 28 viaanother connecting main 43. The connecting mains 42 and 43 are equippedwith air control valves 44 and 45 respectively. The collecting main 37has an air bleeder 46.

In operation, I fire the furnace and push work W therethrough in theusual manner to heat the work for rolling. I also use the recuperator 25to preheat incoming combustion air. I blow cold air from the cooling airmain 32 through pipes 29, 30 and 31 which form the skid sections. Thisair of course is heated as it passes through the pipes. The air thengoes to the collector main 37, from which I can direct it either to thecold air main 26 or the hot air main 28 by proper adjustment of valves44 or 45. In either event it ultimately reaches the burners, where it isutilized as preheated combustion air in con junction with air preheatedin the recuperator. As a further alternative, I can bleed air from thecollector main via the bleeder 46 in the event there is an excess.

From the foregoing description it is seen that my invention affords asimple effective arrangement for cooling the skids of a continuousreheating furnace and overcoming disadvantages of previous arrangements.By forming the skids in sections, I overcome any likelihood of portionsof the skids becoming overheated. Each section receives air while theair is relatively cool. The capacity of recuperator needed is dimnishedsubstantially with a resulting cos-t saving.

While I have shown and described only a single embodiment of myinvention, it is apparent that modifications may arise. Therefore, I donot wish to be limited to the disclosure set forth but only by the scopeof the appended claims.

I claim:

1. In a continuous reheating furnace which includes an enclosure adaptedto have work travel therethrough, burners mounted Within said enclosurefor heating the work therein, a'recuperator, an olftake connecting saidenclosure and said recuperator for carrying products of combustion tothe recuperator, a cold air main connected to said recuperator, and ahot air main connected to said recuperator and to said burners forsupplying preheated combustion air to the burners, the combinationtherewith of a skid construction within said enclosure for supportingthe work, said skid construct-ion comprising a plurality of alignedsections placed end-to-end, each formed of a plurality of pipesextending longitudinally of the enclosure, transverse pipes underneathsaid first-named pipes, and supporting pipes underneath said transversepipes, each of said longitudinally extending pipes having a continuousfixed upper surface, means connected to said pipes for supplying coolingair directly to each of said sections, and means connecting said pipeswith one of said mains for carrying air heated in the pipes to saidburners to be used as preheated combustion air in conjunction with airpreheated in said recuperator.

2. A combination as defined in claim 1 in which said last-named meansincludes a collector main to which said pipes are connected, a mainconnecting said collector main and said cold air main, a main connectingsaid collector main and said hot air main, valves in each of saidconnecting mains, and a bleeder valve in said collecting main.

3. In a continuous reheating furnace which includes an enclosure adaptedto have work travel therethrough, and burners mounted within saidenclosure for heating the work, the combination therewith of a skidconstruction within said enclosure for supporting the work, said skidconstruction comprising a plurality of aligned sections placedend-to-end, each section being formed of a plurality of pipes extendinglongitudinally of the enclosure and support means for said pipes, eachof said pipes hav-- ing a continuous fixed upper surface, a cooling airmain, means connecting the pipes of each section directly to said mainto supply relatively cool air to each section to prevent any portion ofthe skid construction from becoming overheated, and means connecting thepipes of 4 each section with said burners for carrying air heated in thepipes to the burners to be used as preheated combustion air.

4. In a continuous reheating furnace which includes an enclosure adaptedto have work travel therethrough, burners mounted within said enclosurefor heating the work, a recuperator, an offtake connecting saidenclosure and said recuperator for carrying products of combustion tothe recuperator, a cold air main connected to said recuper-ator, and ahot air main connected to said recuperator and to said burners forsupplying preheated combus tion air to the burners, the combinationtherewith of a skid construction within said enclosure for supportingthe work, said skid construction comprising a plurality of alignedsections placed end-to-end, each section being formed of a plurality ofpipes extending longitudinally of the enclosure and additional pipessupporting said firstnam d pipes, each of said first-named pipes havinga continuous fixed upper surface, a cooling .air main, means connectingthe first-named pipes and the additional pipes of each section directlyto said cooling air main to supply relatively cool air to the .pipes ofeach section to prevent any portion of the skid construction frombecoming overheated, and means connecting the pipes of each section toone of said cold air and hot air mains for carrying air heated in thepipes to said burners to be used as preheated combustion air inconjunction with air preheated in said recuperator.

References Cited by the Examiner UNITED STATES PATENTS 1,193,245 8/ 16Dressler 263-6 X 1,515,852 11/24 Ferm 263--6 1,551,945 9/25 Fitch 263-6X 1,634,858 7/27 Stoop 263-6 3,148,868 9/64 Sidwell 263-6 X FOREIGNPATENTS 1,146,514 4/63 Germany.

CHARLES SUKALO, Primary Examiner.

3. IN A CONTINUOUS REHEATING FURANCE WHICH INCLUDES AN ENCLOSURE ADAPTEDTO HAVE WORK TRAVEL THERETHROUGH, AND BURNERS MOUNTED WITHIN SAIDENCLOSURE FOR HEATING THE WORK, THE COMBINATION THEREWITH OF A SKIDCONSTRUCTION WITHIN SAID ENCLOSURE FOR SUPPORTING THE WORK, SAID SKIDCONSTRUCTION COMPRISING A PLURALITY OF ALIGNED SECTIONS PLACEDEND-TOEND, EACH SECTION BEING FORMED OF A PLURALITY OF PIPES EXTENDINGLONGITUDINALLY OF THE ENCLOSURE AND SUPPORT MEASN FOR SAID PIPES, EACHOF SAID PIPES HAVING A CONTINUOUS FIXED UPPER SURFACE, A COOLING AIRMAIN, MEANS CONNECTING THE PIPES OF EACH SECTION DIRECTLY TO SAID MAINTO SUPPLY RELATIVELY COOL AIR TO EACH SECTION TO PREVENT ANY PORTION OFTHE SKID CONSTRUCTION FROM BECOMING OVERHEATED, AND MEANS CONNECTING THEPIPES OF EACH SECTION WITH SAID BURNERS FOR CARRYING AIR HEATED IN THEPIPES TO THE BURNERS TO BE USED AS PREHEATED COMBUSTION AIR.